Capillary electrophoresis-mass spectrometry for top-down protein analysis: development of one- and two-dimensional separation methods and their application in the clinical context

Due to the high sensitivity, selectivity, and the possibility for detailed molecular characterisation, mass spectrometry (MS) is the analytical method of choice for top-down protein biomarker discovery. Due to the low sample consumption, high separation efficiency, and the unique and complementary selectivity, capillary zone electrophoresis (CZE)-MS represents an interesting alternative to the traditionally used liquid chromatography (LC)-MS platforms. In this thesis, instrumental and methodological concepts were developed to increase the potential of CZE-MS for intact proteins. The first part of the thesis describes the development of a nanoflow sheath liquid interface for the efficient coupling of CZE and MS. The interface was developed with a focus on fast setup, easy handling and analytical robustness and has been used for most applications in this thesis. Furthermore, a CZE-MS screening platform for the identification and characterisation of known and unknown Hb variants from DBS samples was developed. The application of SMIL coatings enables efficient separation of closely-related proteoforms and even positional isomers of glycated Hb on the intact level. In the last part of the thesis, nanoLC and CZE-MS were coupled in a heart-cut approach using a polymer nanoliter valve. The platform was used for the glycosylation profiling of heterogeneous alpha-1 acid glycoprotein (AGP). This approach enables the assignment of notably more glycoforms from a lower concentrated AGP sample, compared to CZE-MS alone. In a proof-of-concept study, the platform was further extended to operate in the selective comprehensive mode. With a single injection, 19% more glycoforms were assigned compared to the heart-cut approach with 3 injections. The here presented instrumental and methodological concepts show the great potential of CZE-MS in the context of clinical protein analysis. Especially the combination of LC and CZE in multidimensional separation platforms shows great potential